U.S. patent number 8,282,392 [Application Number 13/104,232] was granted by the patent office on 2012-10-09 for self-ligating orthodontic bracket assembly.
Invention is credited to Jack Keith Hilliard.
United States Patent |
8,282,392 |
Hilliard |
October 9, 2012 |
Self-ligating orthodontic bracket assembly
Abstract
A clip for a self-ligating orthodontic bracket assembly has a
lifting element between the labial surface of the bracket and the
labial portion of the clip that can be rotated to provide a range
of adjustability in lifting the labial portion of the clip with
respect to the bracket. The lifting element thereby controls the
range of motion of the tongue of the clip in its closed position.
This limits the forces applied by the clip to an archwire held in
the archwire slot of the bracket, and also allows an archwire to
slide freely in the slot. A threaded shaft or camming mechanism can
be employed as the lifting element.
Inventors: |
Hilliard; Jack Keith (Lakeland,
FL) |
Family
ID: |
41797519 |
Appl.
No.: |
13/104,232 |
Filed: |
May 10, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20110212407 A1 |
Sep 1, 2011 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
12552854 |
Sep 2, 2009 |
7963768 |
|
|
|
61094511 |
Sep 5, 2008 |
|
|
|
|
Current U.S.
Class: |
433/11 |
Current CPC
Class: |
A61C
7/287 (20130101); A61C 7/22 (20130101) |
Current International
Class: |
A61C
3/00 (20060101) |
Field of
Search: |
;433/2-24 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rodriguez; Cris L
Assistant Examiner: Aponte; Mirayda A
Attorney, Agent or Firm: Dorr, Carson & Birney, P.C.
Parent Case Text
RELATED APPLICATION
The present application is a continuation of the Applicant's
co-pending U.S. patent application Ser. No. 12/552,854, entitled
"Self-Ligating Orthodontic Bracket Clip," filed on Sep. 2, 2009,
which is based on and claims priority to U.S. Provisional Patent
Application 61/094,511 filed on Sep. 5, 2008.
Claims
I claim:
1. A self-ligating orthodontic bracket assembly comprising: a
bracket having: (a) an archwire slot extending mesio-distally
across the bracket for receiving an archwire; (b) a channel
extending through the bracket in an occlusal-gingival direction;
and (c) a labial surface; a clip having: (a) a back forming the
lingual aspect of the clip, sliding within the channel of the
bracket between an open position and a closed position for the
clip; (b) a labial portion; (c) a tongue extending from the labial
portion of the clip across the archwire slot when the clip is in
the closed position, and being retracted from the archwire slot
when the clip is in the open position; and (d) a slot through the
labial portion of the clip; and a rotatable lifting element having
a head adjustably lifting the labial portion of the clip from the
labial surface of the bracket, thereby adjusting the force exerted
by the tongue of the clip on an archwire in the archwire slot;
wherein the slot through the labial portion of the clip provides
access to the head of the lifting element, and has a length
selected to limit the range of travel of the clip between the open
and closed positions.
2. The self-ligating orthodontic bracket assembly of claim 1
wherein the clip is substantially J-shaped.
3. The self-ligating orthodontic bracket assembly of claim 1
wherein the labial portion of the clip is contoured to follow the
contour of the labial surface of the bracket.
4. The self-ligating orthodontic bracket assembly of claim 1
further comprising a stop on the back of the clip preventing the
clip from becoming dislodged from the channel of the bracket.
5. The self-ligating orthodontic bracket assembly of claim 1
further comprising a recess in the bracket adjacent to the archwire
slot for receiving the tongue of the clip in the closed
position.
6. A self-ligating orthodontic bracket assembly comprising: a
bracket having: (a) an archwire slot extending mesio-distally
across the bracket for receiving an archwire: (b) a recess adjacent
to the archwire slot; (c) a channel extending through the bracket
in an occlusal-gingival direction; and (d) a curved labial surface;
and a clip having: (a) a back forming the lingual aspect of the
clip, sliding within the channel of the bracket between an open
position and a closed position for the clip; (b) a labial portion
with a curved contour to slide over the curved labial surface of
the bracket; (c) a tongue extending from the labial portion of the
clip across the archwire slot and seating in the recess in the
bracket when the clip is in the closed position, and being
retracted from the archwire slot when the clip is in the open
position; and (d) a slot through the labial portion of the clip;
and a rotatable lifting element adjustably lifting the labial
portion of the clip from the labial surface of the bracket, thereby
adjusting the force exerted by the tongue of the clip on an
archwire in the archwire slot; wherein the slot through the labial
portion of the clip provides access to the head of the lifting
element, and has a length selected to limit the range of travel of
the clip between the open and closed positions.
7. The self-ligating orthodontic bracket assembly of claim 6
wherein the clip is substantially J-shaped.
8. The self-ligating orthodontic bracket assembly of claim 6
further comprising a stop on the back of the clip preventing the
clip from becoming dislodged from the channel of the bracket.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of
orthodontics. More specifically, the present invention discloses a
self-ligating clip for orthodontic brackets.
2. Statement of the Problem
In the standard practice of orthodontics, a wide range of
armamentarium is required including wires, springs, bands, brackets
and the like. Orthodontic brackets in particular serve as the
central conduit for transferring corrective forces to each
individual tooth. Being rigidly connected to a tooth, corrective
forces are transferred through a bracket and thereby to the root of
a tooth and then to the supporting bone surrounding the root. The
gentle but continuous forces elicit a physiological response in the
supporting bone allowing teeth to slowly reposition. Orthodontic
brackets were developed in the late 1800's, and even though
manufacturing methods and basic configuration have been greatly
improved, the biological functioning of orthodontic brackets
remains unchanged today.
Before proceeding through the history of orthodontic brackets, it
is important to understand the frame of reference commonly employed
in dentistry. The term "gingival" refers to a direction toward a
patient's gingiva or gum. The term "occlusal" is the opposite of
"gingival" and refers to a direction toward the occlusal or incisal
edge of a tooth (i.e., toward the bite plane between the upper and
lower teeth). The term "mesial" (or the adjective "mesio") refers
to a direction toward the mid-line of a patient's dental arch. The
"distal" is the opposite of "mesial" and refers to a direction away
from the mid-line of a patient's dental arch. The term "lingual"
refers to a direction toward the patient's tongue. The term
"labial," as applied to the front teeth, refers to a direction away
toward the lips. The term "buccal," as applied to the bicuspid or
molar teeth, refers to a direction toward the cheek. All of these
terms are commonly used relative to a specific tooth.
The central feature of an orthodontic bracket is an archwire slot,
sometimes referred to as the "slot". Two parallel walls define the
slot feature, and a slot floor is oriented perpendicular to the
walls. The slot feature is oriented horizontally and extends
centrally across the full mesial-distal width of a bracket.
Orthodontists normally place brackets on all of an orthodontic
patient's teeth. The slots open to the labial or buccal aspects to
accept an orthodontic archwire. The archwire spans all of the
brackets by engaging the slot of each bracket. For example, U.S.
Pat. No. 3,504,438 to Wittman et al. discloses orthodontic brackets
with arch slots and an archwire.
It should be understood that it is the relationship between the
arch slot and the archwire that drives correction of tooth
position. Corrective forces are generated by the capturing of an
archwire in a bracket's slot. Doing so usually requires that the
archwire be deflected from its passive arcuate shape, which loads
the archwire as a resilient spring. Loading in this manner causes
potential energy to be stored in the archwire. It is the gradual
dissipation of the stored energy that causes teeth to move into
their desired, finished positions and orientations.
Generally, today's orthodontic armamentarium, and in particular,
orthodontic brackets benefit from a tradition of constant
improvement that has spanned many decades. In order to contain
costs and to make orthodontic treatment more affordable,
orthodontic practices must constantly embrace hardware systems and
procedures that deliver increased efficiency. Hardware systems and
chairside procedures that avoid problems, save time and eliminate
steps must be embraced in order to reduce the total amount of
treatment time required to treat each patient. Today's business
environment requires that orthodontists become successful managers
of their practices as a business as well as being skillful
practitioners. One area that exemplifies the tradition of constant
improvement can be seen in the means with which the orthodontic
archwire is retained in the slots of the brackets. An historical
review of that follows.
As mentioned earlier, orthodontic brackets were developed in the
late 1800's. Beginning then and continuing through to roughly the
early 1980's, archwires were routinely retained in the slots by
tying-in the archwire using ligature wire. During that period,
ligature wire was used in diameters ranging from 0.009 to 0.012 in.
Ligature wire is fully annealed, dead-soft stainless steel
exhibiting an ultimate tensile strength of about 70,000 psi. In the
very soft temper and in those diameters, ligature wire is extremely
malleable and can be twisted into a tight helix. FIG. 7 of U.S.
Pat. No. 4,392,494 to Ashby, shows a typical Siamese-type
orthodontic bracket with an archwire residing in the slot. A
ligature wire engages the four tie-wings and transverses the
bracket, up and over the archwire to tie it in, retaining it
tightly in the slot against the slot floor. After pulling and
twisting the ligature wire as tightly as required, the loose ends
of the wire are cut off. The short, remaining twisted portion is
tucked out of the way, under the tie wings in order to avoid
laceration of soft tissue by the sharp ends. In order to perform
the routine step of changing an archwire, an orthodontist or staff
person must carefully repeat the procedure, usually ten times per
arch, for a total of twenty times.
Steel ligatures have useful qualities that served orthodontists
well. For example, in the case of a highly mal-positioned tooth, a
steel ligature could first be partially tightened in a manner that
avoided high deflection and the tight cinching of the archwire
against the slot floor. At a subsequent appointment, the
practitioner had the option of then fully tightening the ligature.
Such tightening of steel ligatures allowed the progressive
tightening to match desirable tooth movement response achieved over
several weeks, such as the interval between patient appointments.
Had the practitioner fully tightened the ligature initially, the
patient would likely have experienced significant discomfort, and
the resulting higher than optimal forces could have actually
resulted in a slower tooth movement rate. Orthodontic patients
treated with steel ligatures were often scheduled for appointments
where the objective was to simply tighten all of the ligatures.
Such a tightening served to more aggressively transfer stored
energy from the deflected archwire to the brackets and teeth.
Other common procedures took advantage of the characteristics of
steel ligatures. For example, in the case of a highly-rotated
tooth, the practitioner had the option of using only the distal
pair or mesial pair of tie wings for ligation rather than the
conventional use of all four wings. Selectively using only one pair
of tie wings created an advantageous moment in rotation, which was
capable of more effectively correcting a tooth in terms of
rotation. Progressively tightening a ligature that was placed for
rotation was an ideal method for correcting rotated teeth. Steel
ligatures, not being of any set length, could take up the length of
tying two wings or the longer route of four wings. Doctors and
staff became very accustomed to characteristics of steel ligatures
and skills associated with ligation facilitated treatment well.
In cases with teeth generally well oriented in terms of torque and
rotation, but requiring translation to a new position, steel
ligatures once again filled the need well. In those cases, the
bracket and its corresponding tooth would be ligated closely to the
archwire, but not tightly. This would permit the tooth to remain
under the influence of the archwire-archslot relationship while
sliding along the archwire in response to tractive forces such as
an elastic or steel coil spring. During such sliding, the tight but
free-sliding ligature around the archwire would keep the bracket
oriented on track, but the steel ligature would be configured
loosely enough so as to not create excessive binding or undue
friction. Conversely, once the tooth arrived at its ideal position,
the ligature could be fully tightened. Such tightening served to
greatly increase the sliding friction between the archwire and the
bracket. In this way, steel ligatures could be used to allow a
bracket to slide freely to its desired position, then once arriving
there, lock it in place. Such a methodology served well such as in
closing extraction spaces.
Even though dead-soft stainless steel ligatures served quite well
for many years, the shortcomings became more problematic as other
areas of the orthodontic operatory became modernized. Orthodontists
began treating much larger numbers of patients and steel ligatures
did not fit well into the streamlined needs of a fast-paced
orthodontic practice. The amount of time required to change an
archwire became excessive compared to other advancements. After
all, steel ligatures require special instruments, and tying an
archwire to each tooth is time consuming. Further, if each ligature
is not placed with care and not cut and tucked properly, the
patient's tongue, lips or cheeks can be painfully pierced. Even
though steel ligatures are still used today for certain treatment
situations, they have by and large been supplanted by elastomeric
ligatures.
For example, U.S. Pat. No. 6,935,858 (Cleary) shows a typical
orthodontic case with the archwire retained with elastomeric
ligatures. Like steel ligatures, elastomeric O-rings are placed to
hold the archwire fully seated in the bracket slots. Elastomeric
ligatures are non-metallic and are injection molded from
biocompatible, low-durometer urethane resins. Orthodontic
manufacturers typically offer a family of elastomeric products.
Central to such product lines are the ligatures, which can take on
any combination of cross-sectional diameter and toroidal diameter
required to fit a range of narrow-to-wide brackets. The man-made
elastomeric resins used are generally slightly stiffer/harder than
the familiar natural latex "rubber bands" used in orthodontics.
Elastomeric ligatures are typically molded integrally with a
carrier and each ligature is connected to the carrier by a thin
runner or sprue. Once the ligature is hooked over one wing of a
bracket, the practitioner can fail the sprue by pulling the carrier
away. Elastomeric ligatures are also commercially available
individually, along with special placing instruments. As described,
commercial sources of ligatures typically offer a family of
elastomeric products molded from the same elastomer. U.S. Pat. No.
5,461,133 (Hammar et al.) discloses some of the other types of
orthodontic products typically offered along with elastomeric
ligatures, including chains and rotation wedges. Elastomeric
urethane materials are commercially available in many
configurations and sizes as well as a wide array of colors,
including metal flake and glow-in-the-dark versions. Such offerings
allow orthodontic patients the option of self-expression, which is
thought to increase the patient's cooperation with treatment
objectives.
The use of small elastomeric ligatures bypasses the steps of
twisting, cutting and tucking as is required when using steel
ligatures. Each elastomeric ligature is initially caught by one of
the bracket's tie wings and then stretched over the other tie
wings. No additional steps are required to ligate-in the
archwire.
Compared to steel ligatures, elastomeric ligatures do not have
quite as much adjustability and versatility. For example, steel
ligatures were described earlier as allowing a close, but still
sliding relationship between a bracket and an archwire for cases
where teeth must be bodily translated along an archwire. Being
stretched in place between the tie wings and over the archwire,
elastomeric ligatures are always in tension and therefore
continuously urging the archwire against the slot floor. Such
constant working of an elastomeric ligature serves well for
rotating and torqueing teeth, but such forces are not as desirable
when low friction and sliding translation is needed. In most
treatment situations elastomeric ligatures cannot be held off, and
do not allow the option of progressive tightening, and cannot be
adjusted in any way.
In spite of the merits of steel versus elastomeric ligatures, it is
the elastomeric version that has been adopted as today's default
standard by the orthodontic profession due to efficiency and speed.
Orthodontic staff can change-out an archwire much more quickly
compared to the time required using steel ligatures.
Further advancements in the orthodontic armamentarium have resulted
in the self-ligating bracket. Such brackets are designed with newer
features that eliminate the need for any sort of ligature
all-together. The first successfully functioning self-ligating
bracket was developed by Ford, and was disclosed in 1935 through
U.S. Pat. No. 2,011,575. Ford's invention disclosed a bobbin, that
when rotated clockwise aligned with other structures allowing an
archwire to drop into the slot, but after rotating the bobbin
counter-clockwise, the wire is retained. Even though Ford's
self-ligating bracket (known as the "Ford lock") was
commercialized, it did not see widespread popularity. This was
likely because today's impetus for speed and efficiency was not as
critical in Ford's day.
The first self-ligating bracket to achieve widespread commercial
success was developed by a Canadian orthodontist, G. H. Hanson.
Hanson's development was disclosed in U.S. Pat. No. 4,492,573
issued in 1985. Improvements thereto have been disclosed by other
patents to Hanson, such as U.S. Pat. No. 5,586,882. Appropriately,
Hanson's bracket design is marketed as the "Speed Bracket" as it is
known today. The Speed Bracket is very popular with orthodontists
world-wide because it further reduces the time required to
accomplish the task of changing-out an archwire. The Speed Bracket
has an occlusal-gingivally sliding clip. With the clip positioned
occlusally, the bracket is considered to be in the open
configuration to accept an archwire. With the clip positioned
gingivally, the bracket is in its closed configuration to retain an
archwire. Certain features serve to bias the clip in the open or
closed positions.
As a category, self-ligating brackets have become an important
adjunct to today's armamentarium. The designs offered by
orthodontic manufacturers have advanced, overcoming the early
problems such as tartar build-up blocking the smooth sliding of
clips, clips that would not stay open or stay closed, clips that
could become loose in the mouth, and the increased bulk and height
of self-ligating brackets compared to conventional brackets.
When considering the entire category of self-ligating brackets,
they can be further classified into groups based on the mechanical
means for achieving ligation. For example, U.S. Pat. No. 4,712,999
to Rosenberg describes a self-ligating bracket with a cover plate
that resiliently engages a corresponding cylindrical section of the
bracket. Rosenberg's clip is a separate part, and hinges open and
closed once in position. An improvement over Rosenberg is
exemplified by a living hinge. For example, U.S. Pat. Nos.
6,733,286, 6,932,597, 6,960,080 and many subsequent patents to
Abels et al. disclose a ligation cover integrally attached to the
base of the bracket as one piece that moves between an open and
closed position. Yet other innovative means for self-ligation
utilize a true fixed hinge for the clip. Even though depicted as an
adjunct to lingual brackets, U.S. Pat. No. 6,485,299 (Wildman)
discloses such a hinging clip. U.S. Pat. No. 6,984,127 to Ming
discloses a self-ligating bracket based on a resilient latch that
can retain an archwire once an archwire is forced into the
latch.
As can be appreciated, many inventors have contributed improvements
to the field of self-ligating brackets and today there are multiple
categories of such brackets, each delineated by the specific means
used for securing the archwire in the slot. The present invention
is directed to one of these categories of self-ligating brackets.
First, to describe the category:
One example of the relevant category of self-ligating brackets is
taught by U.S. Pat. No. 6,071,119 (Christoff et al.). This bracket
20 consists of a rigid bracket body through which passes a
mesial-distal extending arch slot 30 shown with an archwire 40a
residing in the slot. A one-piece movable latch 32 has a labial
portion 34a and a sliding portion 36a. The bracket body 24 includes
a retentive lip 44a and a stop 46a. The movable latch typical of
this category of self-ligating brackets is usually formed from
spring-temper metal and as such it is biased inwardly, toward the
arch slot, serving to actively restrain the archwire from escaping
from the slot. Such clips may be formed from AISI type 410
stainless steel or 17-7 ph, a stainless alloy. Once formed, sliding
clips can be heat treated to a near spring temper and as such, the
force level required to deflect the labial portion outward can be
significant. As such, the labial portion of the latch can be
considered as "active" in that with sufficient labially or
buccally-directed force, it can flex outward away from the archwire
slot floor to the extent that it is restricted from further outward
flexing by a retentive lip feature 44a of the bracket body
according to Christoff et al.
FIG. 9 of U.S. Pat. No. 7,104,791 to Hanson similarly shows a
movable latch moved to its closed position. The movable latch is
configured similarly to the invention of Christoff et al., having
features that limit the range of lingual-labial or lingual-buccal
flexing of the labial portion, and an inward or lingual spring bias
of the labial portion of the latch.
U.S. Pat. No. 7,186,114 to Navarro et al. shows yet another movable
latch in a closed position (FIG. 4a) and in an open position (FIG.
4c). FIG. 4a depicts the archwire-retaining portion of the movable
latch 38 positioned in its lingual-most position, limited from
further lingual movement by the edge of the recess 48. As can be
appreciated, should treatment forces act on the archwire to lift
the archwire out of its slot 28, the archwire will be urged back
into a seated position in the slot due to the lingual bias and
resilience typically observed in such sliding latches used with
self-ligating brackets of this category. However, if the forces
acting to lift the archwire exceed the resilience of the labial
portion of the latch, the latch can open only to the other end of
its range as defined by the lip of the recess 48. The latch
flexure-limiting function of the recess 48 is substantially
identical to the retentive lip 44a of Christoff et al.
U.S. Pat. No. 7,214,057 to Voudouris shows yet another
self-ligating bracket with a sliding latch. Of importance when
considering the present invention, the reader should note the wide
tongue portion of the clip located generally above numeral 94 in
FIG. 11 of the Voudouris patent. It is important to visualize the
tongue portion as engaging the same sort of retentive lip
functioning as feature 44a and 46a shown by Christoff et al.
The present invention can be viewed as an improved movable latch of
the same general type as those disclosed by these prior art
patents. To best describe and illustrate the benefits and
advantages of the present invention, FIGS. 1-7 show a consolidation
of the sliding latch-type features from these prior art patents
into a hypothetical composite configuration. In particular, FIG. 1.
shows a moving latch 10 that is a composite of the features of the
clips of the prior art patents discussed above. For the purposes of
this disclosure, the terms "clip" and "latch" are used
interchangeably.
FIG. 2 shows the composite sliding latch 10 in place in its closed
position within the body of the composite bracket 20. The tail 16
of the latch 10 is a disrupted feature, usually formed as a press
operation that serves as a stop for the latch 10. The stop limits
sliding of the clip 10 as it reaches its fully open position and
prevents the clip 10 from becoming dislodged from the bracket
20.
As pointed out earlier, during the manufacture of such brackets 20,
the sliding latch 10 is hardened to a near-spring temper and as
such, it maintains a shape that when in position biases the tongue
18 of the clip 10, inward or lingually, as shown in FIGS. 2 and
3.
In FIG. 4, the tongue 18 of the clip 10 is acting on a light, round
archwire 30, urging it lingually, and cinching it against the slot
floor formed in the rigid bracket body 20. Such a configuration is
useful for controlling a pliable, smaller-diameter round wire 30
such as is typically placed by orthodontists early in treatment.
The configuration of the tongue 18 in FIG. 4 enables it to push
lingually against the round archwire 30. Thus, the tongue 18 of the
clip 10 is well positioned to actively capture the archwire 30, and
thereby transfer forces from the archwire 30 to the root of the
tooth.
The meaning of the term "active", as it applies to movable latches,
can be explained as follows. Earlier, steel ligatures were
described and in particular the practice of progressively
tightening steel ligatures with the steel ligature engaging only
one of the two pairs of ligation wings of a standard orthodontic
bracket was described. That practice served as a means for
correcting tooth position in terms of rotation. Later, the
elastomeric ligatures were described as also being capable of
engaging only one pair of the two pairs of tie wings of a
conventional bracket. For self-ligating brackets, rotation
correction is instead pursued using the "active" qualities of the
sliding latch. As can be appreciated, the lingual or inward biasing
of the latch's tongue 18 against a smaller round archwire 30 tends
to trap such an archwire against the slot 21 floor. In cases where
the tooth is undesirably rotated, the spring resilience of the
sliding latch 10 attempts to deflect the archwire 30 into an "S"
shape as it spans the brackets on adjacent teeth, as illustrated in
FIG. 5. By deflecting the archwire 30 in that mariner, it loads the
archwire 30 to de-rotate the tooth.
During actual treatment situations, the latch's tongue 18 may
become angled so as to be in a non-parallel relationship to the
slot floor. Such a deflection may last for several weeks, but as
the tooth slowly responds to these forces and de-rotates toward its
desired orientation, the tongue slowly returns to its parallel
relationship to the slot floor. It is the constant spring-biasing
by the movable latch 10 and its tongue 18 against an archwire 30
that is considered to be the "active" quality. In summary, it is
the labial-lingual flexing, along with twisting as depicted in
FIGS. 5 and 6 resulting from constant dynamic interplay with the
archwire 30 that defines an active sliding latch 10. The commercial
success of such self-ligating brackets of the type taught by the
prior art is due largely to the effectiveness of the active-biased
sliding latches.
Later in treatment, for final aesthetic positioning of the teeth,
orthodontists typically use larger wires exhibiting a stiffer
temper. Such wires are sometimes called "finishing wires".
Finishing wires exhibit a rectangular cross-section profile. One
popular example of the dimensions of such wires is
0.021.times.0.025 in. An example is depicted in FIG. 7. When such
wires are seated in the arch slot of a conventional self-ligating
bracket, the tongue of the sliding latch is held up, further away
from the slot floor. As such, the lingual or inward biasing of the
sliding latch tongue becomes even more aggressive, acting to force
the finishing wire even more forcefully against the slot floor.
Earlier, recess 48 of FIG. 4a of U.S. Pat. No. 7,186,114 (Navarro
et al.) was discussed. The recess 48 in Navarro et al. limits the
range of flexure of the tongue of the sliding latch. As can be
appreciated from Navarro et al., the tongue portion of the latch
may rest on the lingual-most edge of the recess 48 during early
treatment when a small round archwire resides in the arch slot, but
the tongue may rest near the labial-most edge of the recess 48 near
the end of treatment.
The acceptance and wide use of self-ligating brackets represents an
important advancement in orthodontics. There is however one notable
shortcoming in spite of the popularity of conventional
self-ligating brackets. The problem is similar to the lack of
adjustability and versatility associated with the elastomeric
ligatures described earlier. Both elastomeric ligatures and active
sliding latches cannot be regulated or moderated in any way, and as
such they are constantly applying cinching forces to the archwire.
An unavoidable result of such constant working is sliding friction
between the archwire and a tooth/bracket in translation. Excessive
friction between a bracket and an archwire is undesirable in
orthodontics and some researches believe that even slight friction
and hysteresis in the relative movement of the archwire in the slot
can dramatically slow bodily tooth movement. In response to the
friction problem, considerable innovation has occurred as
low-friction and zero-friction bracket designs have been
promulgated. U.S. Pat. Nos. 5,470,228 to Franseen et al. and
5,160,261 to Peterson disclose various innovative features directed
toward reducing such friction. In the orthodontic lexicon, the term
"sliding mechanics" applies to the issues associated with friction
between brackets and archwires and other areas of orthodontic
hardware. It is common for orthodontic treatment plans to
accommodate the extraction of teeth for arch development, and
subsequently, the serial distalization of the upper arch. These are
examples of treatment phases where teeth must be translated bodily
along an archwire and the considerations of sliding mechanics
apply.
In addition to greatly inhibiting tooth translation rate, tight
binding of the bracket to the archwire can also restrict the
mobility of a tooth, causing it to be positioned in an unnaturally
rigid way in its supporting bone. Such rigidity of course prevents
the normal mobility of the root of a tooth within the elastic
periodontal ligament. Such rigidity can undesirably impact blood
circulation and the general vitality of the region of bone
supporting the tooth. The amount of movement of teeth during
eating, speaking and so on would surprise most people, who may have
the impression that teeth are rigid. Quite to the contrary, teeth
naturally wiggle in position in response to forces. The sliding
friction resulting from the stiff resilience of the latch's tongue
acting against the archwire and the additional friction of the
archwire against the arch slot floor can be a significant
impediment to a treatment plan and treatment schedule.
Solution to the Problem
These concerns involving sliding mechanics are addressed by the
present invention. The present invention introduces a means for
regulating the aggressiveness of rotational forces not unlike the
adjustment latitude afforded by steel ligatures described earlier.
The present invention also allows a free-sliding relationship
between the archwire and the bracket. In addition, with the present
invention, the active (and friction-inducing) qualities of the
labial portion of the sliding clip can be selectively restored as
required over the course of treatment by adjusting a rotating
lifting mechanism.
SUMMARY OF THE INVENTION
This invention provides a clip for a self-ligating orthodontic
bracket assembly having a lifting element between the labial
surface of the bracket and the labial portion of the clip that can
be rotated to provide a range of adjustability in lifting the
labial portion of the clip with respect to the bracket. The lifting
element thereby controls the range of motion of the tongue of the
clip in its closed position. This limits the rotational forces
applied by the clip to an archwire held in the archwire slot of the
bracket, and also allows an archwire to slide freely in the slot. A
threaded shaft or camming mechanism can be employed as the rotating
lifting element.
These and other advantages, features, and objects of the present
invention will be more readily understood in view of the following
detailed description and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention can be more readily understood in conjunction
with the accompanying drawings, in which:
FIG. 1 is a perspective view of a conventional clip 10 for a
self-ligating orthodontic bracket.
FIG. 2 is a perspective view of a conventional self-ligating
bracket 20 and clip 10 in the closed position.
FIG. 3 is a perspective view of a conventional self-ligating
bracket 20 and clip 10 in the open position.
FIG. 4 is a perspective view of a conventional self-ligating
bracket 20 and clip 10 in the closed position holding a round
archwire 30.
FIG. 5 is a perspective view of a conventional self-ligating
bracket 20 and clip 10 in the closed position holding an archwire
30 that has been deflected into an "S" shape by a rotated
tooth.
FIG. 6 is a perspective view of the clip 10 corresponding to FIG.
5.
FIG. 7 is a perspective view of a conventional self-ligating
bracket 20 and clip 10 holding a finishing archwire 35.
FIG. 8 is an exploded perspective view of an embodiment of the
present invention showing a bracket 20 having a threaded hole 24 to
receive a threaded lifting element 14.
FIG. 9 is a perspective view showing the embodiment in FIG. 8 after
it has been assembled.
FIG. 10 is a perspective view of the clip 10.
FIG. 11 is a side cross-sectional view corresponding to FIG. 9 with
the lifting element 14 adjusted to raise the tongue 18 of the clip
10 to a passive position.
FIG. 12 is a side cross-sectional view corresponding to FIGS. 9 and
11 showing the lifting element 14 fully threaded into the bracket
20, thereby allowing the tongue 18 of the clip 10 to move to an
active position.
FIG. 13 is a perspective view of another embodiment of a bracket 20
having a hole 27 with camming surfaces 29 to actuate a lifting
element.
FIG. 14 is a perspective view of a lifting element 17 for use with
the camming surfaces 29 of the bracket 20 in FIG. 13.
FIG. 15 is a perspective view of the lifting element 17 assembled
with the bracket 20.
FIG. 16 is a perspective view of the completed assembly of the clip
10, bracket 20 and lifting element 17.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 8-12 show an embodiment of the present invention that employs
a threaded lifting element 14 to adjustably lift the labial portion
of the clip 10 from the labial surface of the bracket 20. This, in
turn, adjusts the force exerted by the tongue 18 of the clip 10 on
an archwire 30 in the archwire slot 21. The major components of
this embodiment are the bracket 20, sliding clip 10, and a
rotatable lifting element 14.
The bracket 20 is shown in FIG. 8. The base has a conventional base
for attachment to a tooth (e.g., by adhesive). An archwire slot 21
extends in a substantially horizontal, or mesio-distal direction
across body of the bracket 20 with an open labial aspect to receive
an archwire. The archwire slot 21 can have a cross-section forming
three sides of a rectangle, as shown in FIGS. 8, 11 and 12, to
better engage an archwire with a rectangular cross-section. A
channel 22 extends through the bracket 20 in an occlusal-gingival
direction behind the archwire slot 21. The labial surface of the
occlusal portion of the bracket 20 has a curved contour to follow
the contour of the labial portion of the clip 10, as will be
discussed below. The bracket 20 also includes a recess 25 adjacent
to the archwire slot 21 for receiving the tongue 18 of the clip 10
in its closed position. The labial surface of the bracket 20
features a threaded hole 24 to engage the lifting element 14.
Preferably, the clip 10 is generally J-shaped as shown in the
perspective view in FIG. 10. The back of the J forms the lingual
aspect of the clip 10 and has dimensions selected to allow the
lingual portion of the clip 10 to slide within the channel 22 of
the bracket 20 between the clip's open and closed positions. A stop
16 is located at the stem of the J to prevent the clip 10 from
becoming dislodged from the bracket 20. The labial aspect of the
clip 10 can be curved to generally match the labial contour of the
curved occlusal portion of the bracket 20. The tongue 18 of the
clip 10 is designed to seat in the recess 25 of the bracket 20 when
the clip 10 is in the closed position, as shown in FIGS. 9, 11 and
12.
The rotatable lifting element 14 has a threaded shaft with an
enlarged head (e.g., a screw or bolt), as shown in FIG. 8. The
threads of the lifting element 14 engage the threaded hole 24 in
the labial surface of the bracket 20. FIG. 9 is a perspective view
showing the embodiment in FIG. 8 after it has been assembled. The
head of the lifting element 14 rests under the lingual surface of
the labial portion of a clip 10, and serves to lift the lingual
surface of the labial portion of the clip 10 away from the labial
surface of the bracket 20. The degree of lift is controlled by
rotating the lifting element 14 clockwise to lower the clip 10 or
counter-clockwise to raise the clip 10.
As can be seen in FIG. 9, the head of the lifting element 14 rests
under the curved lingual surface of the labial portion of the clip
10 when the clip 10 is in its closed position. As the lifting
element 14 is loosened, the head of the lifting element 14 serves
to lift the tongue 18 of the clip 10 to an intermediate or passive
position in the recess 25 in the bracket 20. FIG. 11 is a side
cross-sectional view corresponding to FIG. 9 with the lifting
element 14 adjusted to raise the tongue 18 of the clip 10 to a
passive position. In this passive state, the tongue 18 is incapable
of exerting cinching forces on the archwire 30. Even though the
tongue 18 is poised near the archwire 30 in the slot 21, no
forceful contact occurs except in situations where the tooth is
undesirably rotated. Lacking contact due to rotation, the archwire
30 is allowed to slide freely in the archwire slot 21 of the
bracket 20. The deleterious effects described earlier resulting
from holding the tooth rigidly and lack of mobility are thereby
avoided. Treatment phases requiring translation of the teeth may be
accomplished while still controlling the tooth's orientation and
inclination.
Later in treatment as the aesthetic finishing phase approaches, an
orthodontist may wish to return the bracket 20 to active
functioning. To do so, the lifting element can be threaded further
into the bracket, thereby lowering the tongue 18 of the clip to the
active position shown in FIG. 12, so that the tongue 18 exerts
resilient force on the archwire 30. In this state, the clip 10
functions like any sliding latch of conventional self-ligating
brackets. The tongue 18 of the clip 10 delivers exacting forces to
the archwire 30, serving to position the tooth in its final ideal
position.
Thus, the threaded lifting element 14 can be readily adjusted
inward or outward to achieve any needed balance between passive or
active functioning of the clip's tongue 18 against an archwire 30.
The lifting element 14 shown in FIGS. 8 and 9, can be adjusted as
desired over the course of treatment using a jeweler's screwdriver.
Alternatively, the means for adjusting the threaded lifting element
14 can be a hex-socket Allen-type engagement, torqs, hexagonal bolt
head, Phillips head, or other standard means.
As can be seen in FIGS. 9 and 10, an elongated slot 15 can be
formed in the clip 10 to allow the adjustment features of the
threaded lifting element 14 to be accessible, and to allow the
sliding clip 10 to move between its open and closed positions. This
slot 15 is envisioned as serving dual functions. For example, the
portion of the threaded lifting element 14 protruding into and
above the slot 15 in the clip 10 may also serve as a stop,
establishing the range of the open and closed positions of the clip
10. This auxiliary function may eliminate the need for traditional
means for limiting travel of the clip. Further, the threaded
lifting element 14 may serve to bias the clip 10 in an open or
closed position.
It should be understood that other mechanisms could substituted in
place of the threaded lifting element 14 in the embodiment depicted
in FIGS. 7-12. In particular, any of a variety of screw mechanisms
could be employed to lift the lingual surface of the labial portion
of the clip 10 from the labial surface of the bracket 20.
For example, one alternative shown in FIGS. 13-16 employs a set of
rotational camming surfaces 29 in a radial pattern formed in the
labial surface of the bracket 20 to engage and actuate a lifting
element 17 that is held between the bracket 20 and the lingual
surface of the labial portion of the clip 10. As shown in FIG. 14,
the lifting element 17 in this embodiment has a central shaft that
seats in a hole 27 in the labial surface of the bracket 20, and two
arms 19 extending outward from the shaft. The arms 19 ride on the
camming surfaces 29 arranged in a radial pattern about the central
hole 27. The camming surfaces 29 cause the lifting element 17 to
raise or lower the tongue 18 of the clip 10 as the lifting element
17 is rotated, FIG. 13 is a perspective view of the bracket 20
showing the hole 27 and camming surfaces 29. The lifting element 17
can be progressively adjusted over the course of treatment, if
desired, by rotating the head of the lifting element 17 with pliers
or forceps. The camming surfaces 29 could also be designed so that
the lifting element can be rotated between its active and passive
positions, but will tend not to remain in an intermediate
position.
With either embodiment, the head of the lifting element can have an
oblong or elongated shape as shown in FIGS. 15 and 16 to serve as a
visual indicator. At a glance, the orthodontist or staff can easily
ascertain the bracket's active or passive status from the
rotational position of the head of the lifting element. The head of
the lifting element 17 can also include a hex-socket Allen-type
engagement, torqs, hexagonal bolt head, Phillips head, or other
standard means for rotating the lifting element 17.
These lifting mechanisms can be generalized to include virtually
any type of screw or rotating camming mechanism that can formed or
placed between the labial surface of the bracket 20 and lingual
surface of the labial portion of the clip 10. For the purposes of
this disclosure, the term "lifting element" is intended to
encompass all such mechanisms.
The above disclosure sets forth a number of embodiments of the
present invention described in detail with respect to the
accompanying drawings. Those skilled in this art will appreciate
that various changes, modifications, other structural arrangements,
and other embodiments could be practiced under the teachings of the
present invention without departing from the scope of this
invention as set forth in the following claims.
* * * * *